Manufacture of soap



Patented Nov. 19, 1946 Lyle J. Lofdahl, Chicago, 111., assignor to Industrial Patents Corporatin,.Chicago, 111., a corporation of Delaware No Drawing. Application May 1, 1944,

Serial No. 533,645

Claims.

The present invention relates to the improvement of soaps and, more specifically, it is concerned with the manufacture of soap compositions having improved resistance to discoloration and rancidification.

The deterioration of color and odor in soaps is generally attributable, either directly or indirectly, to autoxidation of unsaturated fatty acid radicals contained in the products in various percentages. The oxidative process is, furthermore, greatly accelerated in the presence of certain metals which apparently catalyze the oXidative reaction. Since hydrogenating the unsaturated functions in the soap stock greatly increases the cost and tends to reduce the desirable solubility of the product, this method of achieving stability has not proven to be entirely satisfactory.

The incorporation of certain types of tin compounds, including sodium stannate, sodium stannite, alpha stannic acid, and others, has been proposed in the prior art as a means for inhibiting the chemical processes resulting in rancidification and discoloration of soap. Although a number of these derivatives inhibit rancidification for satisfactory periods of time, preliminary discoloration has been found to occur prior to odor rancidification.

The main object of the invention is to improve the resistance of manufactured soaps to discoloration.

Another object is to satisfactorily inhibit discoloration and rancidification in soap products while, at the sam time, preserving the fresh soap odor for an indefinite period.

The invention contemplates stabilizing soap by the incorporation of stannic borate therein. It has been discovered that when this compound is incorporated into the soap during the process of manufacture, it is possible to accomplish a substantial improvement in the prediscoloration period of the resulting soap composition. Furthermore, a substantial extension of the prerancidification period over that possible in the use of other tin compounds as inhibitors is obtained. Preferably the invention is carried out by incorporating the reaction product of an aqueous solution of stannic chloride and borax, having a substantially neutral pH, into the soap stock during the process of manufacture. The advantage of adding the agent in this form is that substantially improved dispersion results due to the colloidal condition of the reaction product.

The amount of the agent to be added is dependent on the degree of unsaturation of the raw materials, e. g. fat, in a particular instance.

Generally speaking, the agent may be employed in the proportion of from about 0.003 per cent to 2 per cent based on the weight of the resulting soap product. The upper limit will, in most cases, be governed by economical considerations, whereas the lower limit will depend upon the proportion of unsaturated functions in the raw material. It is preferred to employ from about 0.1 per cent to about 1 per cent of the agent to provide a satisfactory stabilizing action for most The mixture is continuously stirred until it assumes a gel-like condition and, preferably, the pH adjusted to about neutral. The gel product contains about 30 per cent solids and is ready for incorporation into'the soap.

The stannic borate gel formed by the above procedure or stannic borate per se may be added to the soap or soap product at any convenient point in the manufacturing operation. For example, it has been found advantageous to incorporate the agent into the soap stock while in the kettle or the crutcher, prior to framing or before the drying operation. In the case of a toilet soap, it may be added before, after, or during the milling operation, with or without coloring matter, perfumes, fillers and the like. The addition of the agent is preferably accomplished as soon as possible after saponification so as to curtail the formation of intermediate peroxides. As a general rule, the sooner the antioxidant can be added to the soap stock, the more effective the stabilizing action.

In order to obtain a comparison between the effect of stannic borate with known inhibitors on lengthening the prediscoloration period of soap products, a number of samples were prepared from the same lot of soap containing the same amount of stabilizer (0.05 per cent) and the samples subjected to aging treatments to determine the relative deterioration that had occurred during the respective periods. At the termination of the test period, color readings were taken Alpha Sodium Sodium Color of Aged gggg stannic stanstsng; fresh acid nate nito sample I. Six months at room conditions 56. 2 49. 5 43. 7 70. 0 II. Six months at room conditions 59.0 55.3 51.7 43. 6 70.0 111. Two weeks at 45 C s. 73. S 55. 1 79. 8

In Experiment I, the effect of stannic borate is compared with that of alpha stannic acid in a milled soap by aging both samples for 6 months at room conditions. As shown in the table, the sample containing stannic borate showed a material improvement in color over the sample containing alpha stannic acid. Experiment II similarly demonstrates the superiority of stannic boram over sodium stannate and sodium stannite in samples taken from another soap lot. In Experiment III, the eifect of stannic borate on the prediscoloration period of framed soap is compared with sodium stannate. In this case, the samples Were given an accelerated aging test by maintaining them at 45 C. for 2 weeks. It was observed that the sample containing stannic borate showed a very marked improvement in color and odor over the sample containing sodium stannate. In Examples 1 and 2, the agents were added during amalgamation and prior to milling, while in Example 3, the agents were added during the crutching stage of processing.

A soap stock consisting of 83 per cent tallow soap and 17 per cent coconut soap has been stabilized with 0.2 per cent of a reaction product of an aqueous solution of stannic chloride and borax, while being processed in the crutcher. The stabilized soap product maintained substantially the original color for an indefinite period of time.

An outstanding advantage is that stannic borate is a neutral product and, therefore, entirely free from any corrosive action on soap making equipment. In this respect, the agent is superior to alpha stannic acid, stannous chloride and other acid-forming salts which have at least a mild corrosive action on metallic surfaces.

It is obvious that the proportions of the agent employed may be varied over wide limits without departing from the spirit of the invention. Moreover, the specific manner described herein for incorporating the agent into the soap stock is purely for the purpose of illustration and is not intended as limiting the invention.

I claim:

1. The method of stabilizing soap, which comprises incorporating therein stannic borate in sufficient amount to substantially retard deterioration and color formation.

2. The method of improving the color stability of a soap composition, which comprises incorporating therein a small amount of stannic borate.

3. The method of improving the color stability of soap, which comprises incorporating therein during the process of manufacture the reaction product of an aqueous solution of stannic chloride and borax, having a substantially neutral pH,

said product comprising as an essential ingredient stannic borate.

4. The method of stabilizing soap, comprising incorporating therein from about 0.003 per cent to about 2 per cent of stannic borate.

5. The method of stabilizing soap, comprising incorporating therein between about 0.1 per cent and about 1 per cent of stannic borate.

6. A color stable soap product, comprising a body of soap and stannic borate uniformly dispersed through said body in sufiicient amount to stabilize substantially the soap against deterioration and color formation.

'7. A stable soap product, comprising soap and a small amount of stannic borate stabilizer incorporated therein.

8. A stable soap product comprising soap and between about 0.003 per cent to about 2 per cent of stannic borate incorporated therein to stabilize the color.

9. A stable soap product comprising soap and between about 0.1 per cent to about 1 per cent of stannic borate incorporated therein to retard deterioration and color formation.

10. A stable soap product comprising soap and a small amount of the reaction product of an aqueous solution of stannic chloride and borax incorporated therein to retard deterioration and color formation, said product comprising essentially stannic borate.

LYLE J. LOFDAI-IL. 

